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Composition API vs Options API: A Complete Guide to Refactoring and Modern Vue Architecture

In Vue 3, the Composition API emerged as a more flexible and scalable alternative to the traditional Options API. It offers better maintainability and modularity, especially for larger or fast-growing applications.

But here’s the key point: the Options API isn’t deprecated. It remains fully supported and works perfectly well for many real-world use cases.

If you are currently migrating to Vue 3, this information is especially relevant. Understanding when to keep the Options API and when to adopt the Composition API can save you weeks of unnecessary refactoring and help you design a cleaner long-term architecture.

So the big question is: should you refactor your existing Vue 3 codebase from the Options API to the Composition API?

This guide is here to help tech leads, senior engineers, and curious developers evaluate the trade-offs with clarity and practical context. Let’s explore what you stand to gain, and what risks or complexities may appear, when switching to the Composition API.

This guide is written by Epicmax, a Vue.js development agency.
If you need help with frontend migration, book a consultation with our Vue.js expert.

TL;DR

  • ✅ Composition API gives better scalability, reusability, and DX
  • 🛡️ Options API still makes sense for small or stable projects
  • 🤪 Composables make code more testable and modular
  • 🔧 Composition API is TypeScript-native and future-proof
  • ⚖️ You can migrate Vue.js app gradually without rewriting your whole app

🧠 Key Differences: Options vs Composition

Official guidance: For small/medium apps, Options API is fine. For full-scale applications, Composition API is preferred.

🔍 Maintainability: Group Logic by Feature

Options API forces you to split related logic:

// Options API
export default {
  data() {
    return { name: '', email: '' }
  },
  computed: {
    isValid() { return this.name && this.email.includes('@') }
  },
  methods: {
    submit() {
      if (this.isValid) alert(`Submitting: ${this.name}`)
    }
  }
}
Composition API lets you keep everything in one place:
<script setup>
const name = ref('')
const email = ref('')
const isValid = computed(() => name.value && email.value.includes('@'))
function submit() {
  if (isValid.value) alert(`Submitting: ${name.value}`)
}
</script>
Related code stays close — making it easier to read, debug, and extract.

🛠️ Real-World Wins: Modularity & Reuse

Mixins in Options API are often messy:
  • Hidden dependencies
  • Naming conflicts
  • Hard to trace
  • With Composition API, composables are just functions:
// useFormValidation.ts
export function useFormValidation() {
  const name = ref('')
  const isValid = computed(() => name.value.length > 2)
  return { name, isValid }
}

Now you can reuse logic across components, test in isolation, and eliminate conflicts.

🤪 Testing: More Predictable with Composables

  • Options API: test everything via the component
  • Composition API: test logic directly via function
// useCounter.ts
export function useCounter() {
  const count = ref(0)
  const increment = () => count.value++
  return { count, increment }
}

// useCounter.spec.ts
const { count, increment } = useCounter()
expect(count.value).toBe(0)
increment()
expect(count.value).toBe(1)
  • Smaller, faster, and cleaner tests.

📈 Scalability: Cleaner Refactors, Better Architecture

When your app grows, Composition API makes it easy to:

  • Extract feature logic to composables
  • Avoid bloated components
  • Reorganize without rewriting everything

“After migrating our enterprise app, feature velocity increased and onboarding time dropped.”

— Monterail Team

🔐 Ecosystem Fit: Composition Is the Default

Most new Vue tools assume Composition API:

  • ✅ Nuxt 3: <script setup> is default
  • ✅ Pinia: Composable stores
  • ✅ Vue Router 4: useRoute() and useRouter()
  • ✅ VueUse: 200+ utility composables

While Options API still works, many libraries assume you're using Composition API, leading to extra boilerplate when integrating.

🔧 TypeScript: Fewer Hacks, More Safety

Composition API:

  • Native TS support
  • Less boilerplate
  • Better autocomplete
const count = ref<number>(0)
Options API supports TypeScript, but it requires more boilerplate and doesn't provide the same inference and generics support as Composition API:
import { defineComponent, PropType } from 'vue'

defineComponent({
  props: {
    count: Number as PropType<number>
  }
})
You’ll write less code and get better DX.

⚖️ Caveats of Flexibility

Composition API gives you power — but with great freedom comes potential chaos:

  • Devs may organize code differently without conventions
  • Too much logic in setup() can get messy
  • Onboarding becomes harder without structure

✅ Use ESLint rules, layered structure, and naming conventions to stay sane.

🤯 Reactivity Gotchas

  • ref() vs reactive() can confuse beginners
  • Destructuring removes reactivity
  • Don’t forget .value when using ref

Tip: Use ref for primitives and reactive for objects. Avoid destructuring unless using toRefs() or storeToRefs().


Bonus:

const state = reactive({ count: 0 })
const { count } = state // breaks reactivity

// Instead, use:
const { count } = toRefs(state)
Learn more in the official Vue reactivity documentation.

🧠 Team Skillset & Onboarding

Composition API assumes:

  • Deeper JS knowledge (closures, reactivity, function scope)
  • Familiarity with typing patterns (TS)

For junior-heavy teams or short-term projects, Options API may still be faster.

🔄 Migration Strategy: No Need for a Big Bang

Vue 3 lets you mix both APIs. Start small:

  • Write new features with Composition API
  • Refactor old components only when touched
  • Add setup() to Options components to ease in

Bonus: you can train the team gradually — no rewrite required.

🛡️ Using Composables in Options API Components (Hybrid Pain)

In Vue 3, composables replaced mixins — and they only work inside setup().

If your codebase still uses the Options API, using VueUse, Vue Router, Pinia, or even Nuxt utilities becomes awkward. You’ll end up duplicating state, breaking reactivity, or writing glue code just to access core features.

<template>
  <div>
    <p>Current route: {{ currentRoute.path }}</p>
    <p>Window is {{ isLargeScreen ? 'large' : 'small' }}</p>
  </div>
</template>

<script>
import { useRoute } from 'vue-router'
import { useMediaQuery } from '@vueuse/core'

export default {
  setup() {
    const route = useRoute()
    const isLargeScreen = useMediaQuery('(min-width: 1024px)')
    return {
      currentRoute: route,
      isLargeScreen
    }
  },

  data() {
    return {
      foo: 'bar'
    }
  },

  created() {
    // Want to access `currentRoute` or `isLargeScreen` here?
    // Nope — it's not on `this`, it's in the setup return.
    console.log('Cannot access composables from here')
  }
}
</script>
Note: You can access composables in the template and setup() return, but not inside created() or methods() via this. That's because setup() and Options parts run in parallel and are not merged.

🔥 Why This Feels Painful

  • Composables can’t be used in data(), created(), or methods() unless you restructure your code to use setup() too.
  • You lose access to this, so you end up in a weird hybrid state.
  • You’re forced to migrate incrementally anyway, or wrap composables in extra glue code.
  • You might end up duplicating state (some in data(), some from ref()), which creates bugs.

✅ How Teams Typically Respond

  • Copy/paste the composable logic into a method or mixin (bad DX)
  • Wrap composables inside plugins or workarounds (gross)
  • Start using setup() in Options components, which leads to full Composition migration

🛠️ When to Stick with Options API

Keep Options API if:

  • Your project is simple and stable
  • Your team is mostly juniors
  • You don’t use advanced Vue 3 features

Composition API is not a must. It’s a tool — use it when it solves problems.

✅ Final Thoughts

Refactoring from Options to Composition API can bring:

  • 💡 Better modularity & testability
  • ⚙️ Clean, scalable architecture
  • 🗖️ Native ecosystem support
  • ✨ Modern tooling & TS integration

But you don’t need to do it all at once.


Recommended approach:

  • New code? ✅ Use Composition API
  • Existing code? ♻️ Migrate when relevant
  • Simple legacy parts? 🛡️ Leave as-is

Vue gives you the flexibility to evolve at your own pace.

🚀 Try It Yourself

Refactor one component. Create one composable.

You’ll see why more teams are choosing Composition API in 2025 and beyond.

npm create vue@latest
# Choose: "Composition API + <script setup>"
Get started. Stay modern. Grow with Vue.
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